1. Technical Field
The present invention relates to printing apparatuses.
2. Related Art
Inkjet printers (hereinafter referred to simply as “printers”) are known as an example of printing apparatuses. In a printer, ink, which serves as an example of liquid, is contained in an ink cartridge, which is an example of a liquid vessel, and printing can be performed by ejecting ink from an ejection head to a print medium such as printing paper. In this kind of printer, a printer has been proposed that has a function of detecting a decrease in the amount of remaining ink in an ink tank and providing a warning in order to avoid an idle-ejecting state, which is a state where the ink has been consumed and the ink to be ejected has run out (e.g., see JP-A-2013-248789 and JP-A-2010-257446).
The printer described in JP-A-2013-248789 has a configuration in which a prism that reflects light in accordance with the state of remaining ink is provided in an ink cartridge, and a decrease in the remaining ink in the ink cartridge is detected based on a detection signal obtained by receiving reflected light from the prism using a photosensor. Remaining ink detection is executed for every single path, i.e., every time the ink cartridge passes over the photosensor.
The printer described in JP-A-2010-257446 has a configuration in which a piezoelectric sensor, in which the frequency of residual vibration of a diaphragm varies in accordance with the state of remaining ink, is provided in an ink cartridge, and a decrease in the amount of remaining ink in the ink cartridge is detected based on a response signal having the frequency of the residual vibration of the diaphragm. If a decrease in the amount of remaining ink (ink-low) is detected, thereafter the detection of the amount of remaining ink using the sensor is not executed, and the amount of remaining ink is determined by a count value obtained by counting the amount of used ink in a pseudo manner.
The printers described in JP-A-2013-248789 and JPA-2010-257446 assume that an ink cartridge is replaced with a new ink cartridge when the ink has run out, whereas a configuration is not considered in which a user can supply ink to an ink tank fixed to the printers. In the case of the configuration in which the user supplies ink to the ink tank, the initial amount of ink in the ink tank is not always fixed due to the user supplying the ink before the printers provide a warning that the ink has run out, or the amount of the ink supplied by the user varying, for example. For this reason, the printers having a configuration in which the user supplies ink to the ink tank is required to more reliably detect a decrease in the amount of remaining ink, in order to avoid the idle-ejecting state.
Meanwhile, for example, in the case where a sensor for detecting a decrease in the amount of remaining ink is configured to apply a voltage to a pair of electrodes provided in an ink tank and detect a decrease in the amount of remaining ink based on a resistance value between the pair of electrodes, if the detection of the remaining ink is frequently executed and the time for which the voltage is applied to the ink is prolonged, there is concern that the ink is affected thereby, e.g., deposition of the ink occurs. In addition, in the case of executing the remaining ink detection at the time of non-printing, i.e., when the ink is not discharged from a print head, if the remaining ink detection is frequently executed, there is concern that the throughput in printing degrades.